esp-hosted: initial fix for esp32-p4

[mhaberler]

first cut for a fix so WiFi.scanNetworks() works on esp32 with esp-hosted network support

works for me for the M5Stack Tab5

I understand the logic to be as follows:

• the external networking processor C6 also stores the Wi-Fi credentials in its local NVRAM.
• Once the host CPU (p4) sends the start scan command, the C6 is already trying to reconnect to WiFi using its stored credentials and this fails the scan network's call.
• Explicitly deleting the stored credentials before the scan fixes the behavior.
• Once you select the Wifi SSID and store its credentials, the C6 connects to this network and stores the Wifi credentials in its local RAM again.